The mechanism for turning up the plies of a tire carcass and wrapping them around the bead rings usually includes a pair of toroid shaped inflatable turnover bladders located at each end of the drum. Examples of such pairs of bladders are shown in U.S. Pat. No. 3,171,769 to V. E. Henley and R. W. Phillips and U.S. Pat. No. 3,475,254 to V. E. Henley, both assigned to the assignee of the present invention. The construction and operation of the turnover bladders is shown and described in FIGS. 10, 11, 12, 13, 14, and 15, and column 8, line 11 to column 10, line 9 of U.S. Pat. No. 3,171,769, and in FIGS. 25, 26, and 27, and column 2, line 62 to column 13, line 11 of U.S. Pat. No. 3,475,254. Briefly, each turnover bladder is positioned radially inwardly of the bead ring and is inflated with the ends of the carcass plies laying on its top surface so as to carry these ply ends upwardly and around the bead ring. Then, the bladder is partially deflated, and a pushover ring, usually carried by the bead ring carrier, moves in and squeezes the bladder and the turned-over ply end against the carcass.
Other patents, in addition to the two mentioned above, that show various kinds of carcass ply turnover bladders are U.S. Pat. No. 3,692,605 to Cantarutti, U.S. Pat. No. 3,721,600 to Cantarutti, U.S. Pat. No. 3,740,293 to Jones and Cantarutti, U.S. Pat. No. 3,776,793 to Frazier, U.S. Pat. No. 3,184,360 to Nadler et al., U.S. Pat. No. 3,490,980 to Mallory et al., and U.S. Pat. No. 3,833,445 to Mallory et al. The two Cantarutti patents, the Jones patent, and the Frazier patent are of particular interest because they show ply turnover bladders that are also used to apply sidewall pads to the expanded carcass of a radial tire, which is one of the capabilities of the turnover bladder of the present invention. The Cantarutti and Jones patents also show an insert member within the inner marginal portion of the bladder during the various operations performed by the bladder. The present invention also uses an insert member within the bladder, but this insert contacts the bladder only after the bladder has expanded a slight amount toward the bead ring. More distinctions between the apparatus of the Cantarutti and Jones patents and that of the present invention will be evident from the following explanation and description of the present invention.
One of the main problems with past apparatus for wrapping carcass plies around bead rings has been achieving a uniform tight wrapping of the plies, and obtaining a ply wrapping that is free of trapped air bubbles. To accomplish this, it is important that when the turnover bladder is deflated, its top surface be positioned very close to the bead rings so that the carcass plies lying on top of the bladder directly under the bead ring do not have to be lifted very far during the wrapping operation. However, a factor which in the past has stood in the way of such positioning of the turnover bladder is that the bladder must be of a small enough diameter when deflated that it does not interfere with the bead ring or bead ring setting mechanism while the bead ring is being carried over the turnover bladder to place it adjacent the carcass plies at the end of the building drum.
Another problem in achieving tight wrapping of the carcass plies is the fact that the bladder during its initial expansion must pull the ends of the plies axially outwardly away from the drum while lifting them into contact with the bead ring, and then the same bladder must, on further expansion, carry the plies back in the axially opposite direction and over the bead ring. This requires a bladder that expands first in one direction and then rolls back in the other direction. Such expansion has been difficult to accomplish with prior bladders, particularly with regard to controlling the time at which the bladder changes its direction of expansion.